Conventional trim circuits provide compensation to an electronic circuit. The goal or purpose of a conventional trim circuit is typically to increase an accuracy of a respective circuit by reducing or eliminating a source of error via a respective trim signal.
An example of a trimmable circuit is an operational transconductance amplifier. One source of error associated with an operational transconductance amplifier is the offset current present on the output. If set properly, trim current can be used to negate the effects of the offset current of the operational to around zero.
In certain instances, it is necessary to produce a very small trim current because a respective error source to be corrected is very small. However, a small current is not easy to generate, since it would imply, for example, a strong scaling of a bandgap current (IB=VBG/R). Such a scaling can be done via either a large resistor and/or with a current mirror having a huge aspect ratio, both of which are undesirable.